Adolescent overweight and obesity are of great and increasing concern in the US. Although comprehensive moderate-to-high intensity behavioral programs produce short-term, modest weight reductions in youth, there are no models for practical implementation in readily-accessible settings to translate promising treatment approaches into practice. High schools are well-positioned to deliver such interventions. They have the facilities and staff to deliver a physical activity program, school nurses with the skills to address obesity, and easy access for adolescents. This application builds on a randomized trial (NIH R21HD053371) of a minimal- intensity, 6-session, school nurse-delivered counseling intervention that engaged adolescents and improved key self-reported weight-related behaviors. Having demonstrated feasibility of implementation and short term behavioral improvements from this modest intervention, we now propose an 8-month, expanded intervention that further leverages existing school-based resources to assess longer term behavioral effects as well as key health outcomes, including BMI. This moderate-intensity intervention includes a structured after-school exercise program delivered by school staff, weekly weigh-ins, and school nurse visits across the entire school year. We will test this higher intensity program's feasibility and ability to reduce BMI and to improve dietary quality, physical activity, and sedentary behaviors in overweight and obese adolescents. One in each of four matched pairs of high schools (8 schools in all) will be assigned to either: (1) Lookin'Good Feelin'Good (LGFG) program -- six 30-minute individual student-centered counseling sessions delivered by school nurses during the first two months followed by weekly weigh-ins and monthly visits over the subsequent 6 months, plus a school-based exercise program 3 times weekly for the full 8 months, or (2) Information attention-control (IC) comparison condition - six individual sessions with the school nurse over the first 2 months followed by monthly visits over the remaining 6 months to check weight and behavior changes and provide pamphlets on weight and weight management. We will recruit 136 adolescents (17/school) in grades 9 through 12 who are overweight or obese (>85th percentile for age/sex) and conduct baseline and 8-month assessments. Our primary aim is to determine the feasibility and efficacy of LGFG compared to IC in reducing BMI. Secondary aims include: determining the effect of the LGFG on adherence to behaviors that mediate BMI change (i.e., dietary quality, physical activity, sedentary behavior) and on secondary physiologic (waist circumference, body fat, blood pressure, lipids, and insulin sensitivity) and psychosocial (e.g., self-efficacy, quality of life, and depression) outcomes. Extending the intervention time-frame and adding an accessible exercise program to our previous, well-accepted program should enable us to achieve both statistically and clinically significant weight loss. This school-based weight management intervention, leveraging existing infrastructure in an accessible setting, has tremendous potential for wide-scale dissemination with significant public health impact. PUBLIC HEALTH RELEVANCE: Adolescent overweight and obesity have increased dramatically in the past several decades. High schools are well-positioned to deliver weight loss treatment to overweight and obese adolescents, as they have the facilities and staff to deliver a physical activity program, school nurses with the skills to provide counseling, and are easily accessible by adolescents. This exploratory study will test the feasibility and ability of a school- based intervention, consisting of school nurse counseling and a school-based exercise program, to reduce BMI and improve dietary quality, physical activity, and sedentary behaviors in overweight and obese adolescents. If effective, this could prove to be a cost-effective and relatively easy intervention to disseminate widely for significant public health impact.